A capsule on a first privately-run resupply mission successfully linked up Wednesday with the International Space Station, the US space agency NASA said.

A robot arm operated by two of the six astronauts aboard the space station snatched the unmanned Dragon capsule at 1056 GMT, more than thirty minutes ahead of schedule, it said.

The docking was completed at 1303 GMT after the ISS crew inspected the capsule's condition with the help of cameras, NASA said.

SpaceX, the private company owned by billionaire entrepreneur Elon Musk, launched the Dragon Sunday evening atop a Falcon 9 rocket from an air base in Cape Canaveral, Florida near the Kennedy Space Center.

The mission was the first of a dozen ISS supply runs that NASA has contracted out to SpaceX under a four-year, $1.6 billion contract, fulfilling a role once carried out by NASA's now retired shuttle fleet.

The capsule is loaded with 882 pounds (400 kilograms) of equipment and material for scientific experiments that will be conducted by an ISS crew commanded by American astronaut Sunit Williams.

The cargo also includes food, clothing and other necessities for the international crew, which besides Williams includes three Russians, a Japanese and another American astronaut.

Dragon is currently the only spacecraft capable of ferrying cargo from the space station back to Earth, and on its return voyage scheduled for October 28 will carry back 1,240 pounds (562 kilograms) of equipment and material.

It is supposed to land by parachute off the coast of southern California.

NASA has been relying on Russian spacecraft for the last year, after retiring its fleet of shuttles -- but the Soyuz craft does not have room for cargo on the return flight.

SpaceX's May mission -- a nearly flawless nine-day test flight to deliver cargo to the $100 billion orbiting station -- marked the first time a commercial outfit had sent its own capsule there and back.

SpaceX says it has 50 launches planned -- both NASA missions and commercial flights -- representing about $4 billion in contracts.

So far, SpaceX has only sent unmanned flights into orbit, but the company aims to send a manned flight within the next three or four years. It is under a separate contract with NASA to refine the capsule so that it can carry a crew.